Pulverizer



A.C.DANKS Jan. i3, 1931.

PULVERIZER Filed Sept. 5, 1929' 2 Sheets-Sheet 2 INVENTOR Patented Jan.1 3, 1931 ALFRED C. BANKS, OF CLEVELAND, OHIO IULVERIZER Applicationfiled September 5, 1929. s r 390,515 I The invention relates topulverizers, and

more particularly coal ulverizers, although the machine may be app iedto the pulverizing of rock or other-solid material which it'is desiredto bring to a finely divided condition. Heretofore, two main types ofmachines have been used in pulverizing coal, the ball machine, and theimpact mill. The ball mill. operates at a relatively low speed and at alow' pockets form in the drum, which leads to irregular burning, whenthe mill is used below maximum capacity. The impact mill, on the otherhand, works at a high speed, as compared with the ball mill, and theimpact of the arms or paddles on the fuel and the impact of particles offuel or other particles eiiects the necessary pulverizatiom In th1s millonly a part of the air required for combustion is used to carry the fuelthrough the mill, and this feature permits a flexibility of operation,since the amount of carrying air may be regulated to correspond to thequantity of fuel being reduced. This form of pul-.

verizer also gives complete control ofthe fineness of the productdepending on the speed at which the material is fedto and, through themill. This form. of mill has the disad- 9 vantage that the powerconsumed per ton of material is high compared with the ball mill,

and the cost of maintenance is high due to the high speed operation andto the abrasive action of the coal upon the parts of the machine.

The object of the present invention is to provide an apparatus havingtheadvantages of both the ball mill and the impact mill without thedisadvantages of either. The apparae tus uses balls, as in the ballmill, and operates at a relatively slow speed. At the same timeprovision is made for controlling the fiowof coal and air through thedrum in such manner that only; a small proportion of the total airrequired for combustion is used as carry ing air. This gives the samefle'xibilit of operation as with the impact mill and the same capabilityof operating at any desired'capac- 1ty without any reduction in theefiiciency of the apparatus or in'the' uniformity of fuel feed. 'Oneembodiment of the invention is shown in the accompanying drawings, wherein: i o

Figure 1 is a longitudinalsection through V the apparatus. Fig. 21s atransverse section 00 V on the line 'IIII of Fig. 1. Fig. ,3 is a transverse section on the line III-'-III of Fi -1. tAnd Fig. 4 is a sectionshowing a modi caion.

Referring tothe drawings, 1. isa cylindrical steel shell, preferably aboiler plate in which are placeda series of castings 2 made. in sectionsso as toform a complete ring running at right angles to the axis ofrotation of thepulverizer. These castings may be chilled 7 castiron,manganese steel, 'or any othermaterial made for the purpose ofwithstandin abrasion. They maybe placed in any desired number and of anydesired diameter, and may be placed either in a straight line or theymay 7 be placed inincreasing or decreasing diameters from the inlet endof the pulverizer, as seen fit. f i i In these grooves are placed ballsAof large diameter, a sufiicient number being placed in so each groove toinsurepulverization of the materialthat passes from. one stage to theother,*the largeballs being placed near the inlet. Thenumber of balls inthese'grooves and their size will depend upon "the size'of the unitunder consideration, but the purpose of the balls and the groove is toget as lar e surface contact between the balls and tile groove aspossible rather than to depend upon the line, contact that is secured inthe ordinary ball mill, when the ballstouch each other in the normalprocess of revolving with the shell. I 1

The small amount carrying air, as it has been termed, up to possibly 10er cent'of the total required, is admitted t rough the feedplate 3 andthrough the space 4, and under some conditions, arrangements may be madefor adjustments at" these points to govam this air. This air, in turn,moves through the pulverizer passin between the ends of the castings 2and t e edges of the diahragms 5 fastened to the drum 6. The eight ofthese diaphragms 5 may be varied to regulate the flow of air andmaterial through the mill and thus increase or decrease the speed ofmaterial passage from one coal stage to the other. This how causes thematerial to leave the first stage after it has become filled. pass overthe e ge of the castings through the ga 7 and fill the second stage andprogress in a ike manner throughout the entire unit, until it reachesthe final sta e. Here it asses the last diaphragm 5 an discharges'trough ports 9 in the drum. The shell 1 is sup orted from a second lar ershell 10, also 0 boiler plate by means of t e spreaders 11 and bolts 12,and the space thus provided between the two sheets const tutes apassageway for the main body of air required for combustion, such airflowing in through the annular openings 13 and 14' and past the fan 15through the pipe 16 to the point of combustion. The mixture of air andpowdered fuel from the ports 9 is thus mixedwith the main body of airflowing inward from the opening 14 to the end of the pipe 16. The fan 15may be located at any point along the line of flow and is driven from amotor 17 mounted on the base 18, such base being in turn mounted on themain supporting base 19.

In the event of the speed becoming such that there becomes a tendencyfor the balls to leave their rooves when carried above the center lineof 51c mill, additional diaphragms 8a of suitable cast material and madeup in sections are bolted to the drum 6 that will prevent this action.These may be substituted, if necessary, for the discs 5 and used bytheir varying lengths to determine the flow of material through the millin the same manner as referred to under the discs 5.

The feed plate 3 is of the usual type comprising alternating bars andslots and is driven from the motor 20 through the gearing in the casing21 and the speed changing means comprising the pair of stepped pulle s22, 22, the belt 23, the worm wheel 24, t e shaft 25, which carries theplate 3, and a worm carried by .the shaft which carries the upperstepped pulley 22. The coal is fed from the hopper 26 by gravity pastthe plate 3 andthrough the inclined pipe therebeneath. H The shell 10 isprovided with a head 27 which may be removed topermit the removal of thedrum 6, such drum being carried on a separate head 28, which isremovable for repalrs. The outlet pipe 16 is supported on the motor base18 by means of brackets 29, 30, with a suitable joint at 31, whichallows the head 27 to revolve while the pipe 16 is stationary, suitablemeans being provided to make the joint tight. The drum 6 and its discsor diaphragms 5 and 8a are attached rigidly to the shell 1 throu h thehead 27 and revolve with the shell. T e diaphragms or discs 5 and 8a maybe replaced by 0t ers of varyin diameters to give varying flows of airan material through the mill, epending upon the conditions encountered.

Fig. 4 shows a construction in which the discs 5 are omitted, and ifdesired, with the mill runnin at a speed low enough to avoid displacingt e balls from their runways, the discs 8a may be dispensed with, thediscs 5 serving by themselves to give the desired restriction to theflow of material and air through the annular space between the drum 6and the runway castings 2.

A wear plate 32 is shown at the inlet end of the mill and is fastened tothe front head 33, which is removable from the shell 1 to provide accessfor repairs or for replacing the castings 2.

When desired, air of high tem erature or preheated air may be sup lied trough the mlet 13, which expedient acilitates the drying of the coal, sothat a more effective pulverizing action is secured in the runwayscarrying the balls. It will also be understood suitable dampers ma beprovided when desired to control the ow of carrying air and the mainbody of air which is independent of the supply of carrying air.

The shell 10 and parts carried thereby are rotated from the motor 20which drives the shaft 34 through the intermediary of suitable reductiongearin in the casing 21. The shaft 34 is provi ed with a gear 35 whichenga es the s ur gear 36 secured to the shell 10. he shel 10 1s alsoprovided with bands 37, 37 engaged by a series of rollers 38, 38 carriedby shafts 39 mounted in suitable bearings 40 mounted in the base casting.19. The form of feed mechanism for supplying the coal to the drum isimmaterial insofar as the present invention is concerned, and the feeder3 may be replaced with an one of the standard commercial feeders whichare available. such as a belt section to which a variable speed drivemay be applied.

What I claim is:

1. In combination in a coal pulverizer, a drum mounted for rotation andprovided on its interior with a series of annular ball races,

a set of balls mounted in each race, means for rotating the drum, meansfor supplying the coal to be pulverized to one end of the drum, a series0 diaphragms arranged in spaced relation longitudinally of the drum withtheir peripheries spaced away from the walls of the drum, an air inletto the end of the drum to which the coal is sup lied, an outlet conduitleading from the ot er end of the drum, means for causing a flow of airtherethrough to conduct from the drum a mixture of pow- .dered coal andair, and an annular inlet passage around the drum extending longitudina1y thereof and communicating with the ios let at the end of thedrum sothat additional air is supplied at this point to the mixture of gowderedcoal and air flowing into said con-' uit.

2. In combinationin a coal pulverizer, a drum mounted for rotation andprovided on 1 its interiorwith a series of annular ball races, a set ofballs mounted in each race, means for rotatin the drum, means forapplying the coal to e pulverized to one end of the drum, asecond druminside the first drum with which the first drum communicates atitsoutsaid conduit.

an; first let end, a series of diaphragms arranged in spaced relationalong .the second drum with "their peripheries spaced away. from thewall fthef. first drum, an air inlet tothe end of ,tl'et leading fromthe other end of the drumxin opposition to the end of the second drui'ngand an annular inlet passa e aroundthe first-drum extendinglongitudina'lly thereof and communicating with said outlet at the end ofthe drum sothat addiq tional air is supplied at this point to themixture of powdered coal and air flowing into an inlet leading from theatmosphere to the mixing chamber for supplying additional air theret Intestimony whereof, I have hereunto subscribed my name this 31st day ofAugust,

1929. a i I no ALFRED o. DANKS.

first drum to which the coal is supplied,

3. In combination in a coal pulverizer, a g

drum mounted for rotation and provided on its interior with a series ofannular ball races, a set of balls mounted in each race, means forrotatin the drum, means for supplying the coal to be pulverized to oneend of the drum;

a second drum inside the first drum with which the first drumcommunicates at its outlet end, a series of diaphragms arranged inspaced relation along the second drum with their peripheries spaced awayfrom the wall of the first drum, a mixing chamber into which the end ofthe second drum discharges,

an air inletto the end of the first drum to whiclithe coal is supplied,an outlet leading rotating the drum, means for supplying the coal to bepulverized to one end of the drum,

a second drum inside the first drum with which the first drumcommunicates at its outlet end, a series of diaphragms arranged in'spaced relation along the second drum with their peripheries spaced awayfrom the wall of the first drum, a mixing chamber constituting anextension of the end of the first drum into which the end of the seconddrum discharges, an exhaust fan located in said chamber, an air inlet tothe end of the first drum to which the coal is supplied, an outletleading from said mixing chamber in opposition to the end of the seconddrum, and

